In a system including a touch screen and an active stylus (which is hereinafter referred to a stylus), the touch screen is subject to noise at some frequencies. In practice, the touch screen needs to avoid work at a frequency with loud noise, and a frequency with low noise (that is, a target frequency) needs to be selected as the operating frequency of the touch screen. Likewise, the stylus should send signals to the touch screen using other frequencies instead of those with great noise, and may send signal using the same frequency of the target operating signal of the touch screen.
To ensure that the touch screen and the stylus operate at the same target operating frequency, generally a suitable operating frequency may be selected for the stylus by a user. For example, the user may select a suitable operating frequency by means of keys. For example, the user presses the key once to switch the operating frequency once, until the touch screen normally makes a response to the operation of the stylus. If a response is made, it means the touch screen and the stylus operate at the same target operating frequency. However, in this method, the user needs to manually adjust the operating frequency of the stylus.
To prevent manually adjustment of the operating frequency of the stylus, improve user experience and accommodate smartness-orientation of the products, an automatic adjustment mechanism is set in the related art. That is, the target operating frequency of the stylus is determined by means of communication between the touch screen and the stylus. This automatic adjustment mechanism specifically included: respectively detecting noise information at a plurality of operating frequency of the stylus by the touch screen; and determining the target operating frequency according to the noise information by the touch screen. The touch screen sends the target operating frequency to the stylus in the form of pulse signal, and adjusts the operating frequency of the stylus to the target operating frequency, such that the stylus and the touch screen operate at the same target operating frequency.
Although no manual operation is needed in the above method, two problems are present:
1. According to the mechanism of orthogonal demodulation, in the process of the automatic adjustment, if the frequency at which the touch screen sends a pulse signal is different from the currently selected operating frequency of the stylus, the stylus may fail to receive and demodulate the code of the target operating frequency correctly.
2. If the frequency at which the touch screen sends a pulse signal causes great noise on the touch screen, the stylus may fail to receive and demodulate code information of the target operating frequency correctly.
Therefore, in the system including a touch screen and a stylus, how to provide a method for determining a target operating frequency of a stylus to overcome the above defects is a problem to be urgently solved in the touch technologies.